1. Field of the Invention
The present invention relates generally to traction improving devices and, more specifically, to devices for improving and enhancing the traction of vehicular tires.
2. Description of the Prior Art
Tires are used as the traction means between the great majority of vehicles and the road, ground or other surfaces to be traveled over. These tires are typically made of rubber or rubber-like material and are frequently filled with air to give them buoyancy and flexibility. Tires almost universally include traction ridges and crevices known as treads which extend circumferentially along the surface of the tire which contacts the surface over which travel is intended. These treads provide the main element of traction between the tire and the travel surface under normal conditions. However, there are conditions under which the treads are ineffective to provide sufficient traction between the tire and the surface. Especially in conditions when the surface is covered with ice and snow, the treads tend to become ineffective in maintaining efficient traction with the travel surface. Under such conditions the predominantly utilized method of improving traction is the use of chains.
Tire chains, or equivalent additions to the tire surface, increase traction by providing a deeper and more irregular road engaging surface on the tire. These chains dig deeper into the snow or ice, and, because of their irregular surface, provide better traction than would the typical, relatively smooth, surface of the tire treads. Although devices such as chains are not desirable under normal conditions since they provide for a rougher and less regular ride, their increased traction abilities make them invaluable under rough weather conditions.
Although most of the prior art chains and similar devices are effective in providing reasonable traction under snowy conditions, there have been several disadvantages which have accompanied the use of such devices. Foremost among these is the difficulty of installation on a tire. A typical prior art tire chain must be worked around the tire by hand and then fastened to itself both on the side of the tire nearest the axle and on the outer side of the tire. Both the process of working the chain around the entire tire, especially when a part of the tire is supporting the weight of the vehicle, and the necessity of working on the inside sidewall of the tire, that is the side surface of the tire which faces the axle, are difficult in the typical outdoor, inclement weather, conditions of installation. Since it is not at all infrequent for the installation of tire chains to take place in a snowstorm on a mountain road, it is desirable that the installation of such chains be as easy and as rapid as possible.
Another difficulty which frequently hampers the use of tire chains is the irregularity of the ride upon such chains. Typical prior art chains consist of a number of links of chain crossing the tread at various intervals along the circumference of the tire. Consequently, the ride on such tire will be bumpy in that when the weight carrying portion of the tire rests specifically on the chain the vehicle will be displaced further from the travel surface than in the intervals wherein the weight of the vehicle will rest on the tire surface itself.
Various attempts have been made in the prior art to solve these difficulties. With respect to the difficulty of installation, and in particular to the difficulty of placing the chain in position circumferentially around the tire, some of the more notable of the prior art devices are described in U.S. Pat. No. 2,608,234, issued to Hughes, U.S. Pat. No. 4,042,000, issued to Nyland, U.S. Pat. No. 4,093,012, issued to Detwiler, and U.S. Pat. No. 4,055,210, issued to Mongault. Each of these prior art references indicates a method by which the chains may be held in place by a device attached to the tire during installation such that the tire may be driven forward on the chain and the motion of the tire causes the chain to wrap around the tire to form a complete web.
The disadvantage of having to work with chains on the interior sidewall of the tire has led to the attempts disclosed in U.S. Pat. No. 1,672,019 issued to F. H. Barber, and U.S. Pat. No. 2,462,378 issued to Fox, to obtain solution. The Barber and Fox inventions relate to a manner in which the final connection can be made on the outside surface of the tire such that it is not necessary to do careful and fine work on the relatively inaccessible interior sidewall.
With respect to the disadvantage of rough and inconsistent ride caused by prior art chains, the most significant attempts to solve this problem known to the inventor are disclosed in U.S. Pat. No. 4,111,251, issued to Bula, and U.S. Pat. No. 3,955,610 issued to Freeman, the present inventor. These patents describe tire chains designed so as to evenly distribute the chains such that the chain support is approximately equal at all points during the tire's rotation.
None of the prior art attempts are entirely successful in solving all three of these problems. A disadvantage in the prior attempts to create self-installing tire chains is that all utilize devices which have the further disadvantage of being frictionally held against the side of the tire. When the tire is then rotated under a load, as in use, the pressure and friction of the devices against the sidewall create pressure imbalances within the tire and abrasion to the portions of the sidewall contacting the devices. This is particularly true when such devices are used on radial tires wherein the shape of the sidewall varies significantly during the rotation of the tire depending on the weight being carried by that portion of the tire. Furthermore, the attempts to solve the difficulty of working with the interior surfaces of the tire when installing the links have not been satisfactorily solved in conjunction with the use of the self-installing device in that none have appeared in the prior art. Finally, none of the prior art attempts to create a smooth ride by providing a constant surface displacement have succeeded in providing both adequate traction for forward travel and an appropriately smooth ride.